The present invention relates generally to the truing of spoked wheels and, more particularly, to an apparatus for adjusting the tension at each spoke of a wheel in a manner that aligns the rim of the wheel to a generally flat reference plane that is perpendicular to the central axis of the wheel.
Spoked wheels are used to provide rolling support for bicycles, tricycles, motor bikes, motorcycles, mopeds and various other types of vehicles. In a typical application, the spoked wheel comprises a centrally located hub which is generally cylindrical and disposed coaxially with an axle. The hub and axle are generally attached in such a way that the hub is free to rotate about the axle. Usually, the hub and axle are associated with an antifriction bearing mechanism disposed between them. Therefore, when the axle is rigidly attached to the frame structure of a bicycle or the like, the hub is free to rotate about the centerline of the axle.
The hub of a spoked wheel generally has two flanges with one flange being disposed at each axial end of the cylindrically shaped hub. The flanges are generally perpendicular to the central axis of the hub. Each of the hub flanges has circumferentially spaced holes through which wire spokes can be threaded or laced. In a typical application, each of the spokes is provided with a right angle end portion which extends through a hole in one of the hub flanges. Furthermore, each spoke is generally provided with a shaped end that prevents its end portion from being pulled through the hole in the hub flange.
A spoked wheel is also provided with a rim that is disposed coaxially around the hub with each portion of the rim being disposed a generally identical radial distance from the central axis of the axle. Each of the spokes extends outwardly from the hub flange and through one of a plurality of holes in the rim. In a typical application, the spokes do not extend in a direction which is perfectly radial from the axle. Instead, each of the spokes extends tangentially from the hub flanges.
The radially outward end of each spoke is attached to the rim of the wheel by the use of a nipple. Although the particular design of the nipple can vary from one application to another, it serves the purpose of preventing the radially outward end of the spokes from pulling away from the wheel's rim. Usually, the nipple is provided with a head portion that is disposed proximate the radially outward surface of the rim. The head of the nipple is made in such a way so as to prevent its passage through the hole, in the rim, through which its associated spoke extends. A tubular portion of the nipple extends radially inward through the whole and is provided with a centrally located threaded hole. The radially outward end of each spoke is threaded and can thus be attached to the rim by screwing the nipple onto the threaded portion of the spoke.
During initial manufacture of a spoked wheel and during subsequent alignment of the wheel, screwing the nipple onto the spoke has the affect of increasing the tension on the spoke and reducing the radial distance between the rim and the central axis of the axle. Furthermore, since the spokes extend from both hub flanges toward the rim, the spokes do not extend from the hub to the rim in a plane that is perpendicular to the central axis of the hub. Instead, each spoke is disposed at a slight angle between the hub flange and the rim since the plane of the rim intersects the hub at a point generally midway between the hub's flanges. Therefore, when the tension on the spoke is increased by threading the nipple onto the spoke, the portion of the rim attached to the spoke is pulled in a direction that has components in both perpendicular and parallel directions relative to the central axis of the hub and axle.
A spoked wheel can become misaligned either during initial manufacture or through subsequent use. Misalignment of a spoked wheel can be indicated by either one or both of two situations. First, the rim of a misaligned spoked wheel can exhibit a noncircular shape in which portions of the rim are disposed at different radial distances from the central axis of the hub than other portions of the rim. This condition can result in the rim being generally oval instead of circular. A second indication of a misaligned wheel is that the position of the rim is in a plane which is not perpendicular to the central axis of the hub or, alternatively, the wheel has a misshapen rim that cannot be defined by any single reference plane. Since the tension of each spoke determines the radial and axial position of the rim portion attached to that spoke, a misaligned wheel can generally be corrected by properly adjusting the tension of its spokes.
Various means for assembling, tightening and truing spoked wheels are known to those skilled in the art. U.S. Pat. No. 3,620,281, which issued on Nov. 16, 1971 to Hasegawa et al., discloses an apparatus that comprises a ring-shaped spoke inserting portion that is provided with slots into which the spokes of a provisionally assembled wheel are inserted. Driver devices, equal to the number of nipples and threadedly mated with the tips of the respective spokes of the wheel, are positioned to oppose each of the slots of a lower assembly at its outer peripheral position and are reciprocable in the directions of the spokes. The principal objective of this apparatus is the fastening of the spokes by clamping the rim and fastening the nipples with a constant torque. Torque motors are mounted on a base and are automatically stopped when a predetermined maximum load is applied to each nipple. A disadvantage of this type of apparatus is that, in many instances, a perfectly aligned rim will require different torques on each of the nipples of the spoked wheel.
U.S. Pat. No. 3,631,577, which issued on Jan. 4, 1972 to Hasegawa et al., discloses a machine for provisionally assembling wire spoke wheels. It comprises a rim positioning table that is rotatably mounted with a hub supporting cylinder. Nipples are automatically supplied to a driving means and mated with the threaded tips of the spokes. This type of machine is applicable for the initial assembly of spoked wheels, but does not provide a means for assuring the correct alignment of the rim or the proper tension on each of the spokes.
U.S. Pat. No. 3,758,931, which issued on Dec. 29, 1971 to Patterson, discloses a wheel assembly apparatus in which a bicycle wheel rim is placed on a fixture that is mounted on a rotary index table. A plurality of spokes are attached to the hub of the wheel. The hub is spun in order to cause the spokes to be centrifugally positioned in a substantially uniform angularly spaced relation. A portion of the device extends nut-like threaded fasteners, or nipples, through the holes in the rim and tightens the nipples onto the end portions of the spoke. This type of device is appropriate for use during initial assembly of spoked wheels, but does not provide a satisfactory means for assuring that the wheel's rim is properly aligned with respect to the central axis of the hub.
U.S. Pat. No. 3,840,965, which issued on Sept. 15, 1972 to Meiklejohn, and U.S. Pat. No. 4,187,895, which issued on June 23, 1976 to Saruwatari et al., both disclose apparatus for the manufacture of spoked wheels. These machines provide for the automatic assembly of wire spoked wheels, but do not provide a truing apparatus for the proper alignment of the wheel. Similarly, U.S. Pat. No. 3,636,614, which issued on Jan. 25, 1972 to Damman et al., and U.S. Pat. No. 4,427,047, which issued on Jan. 24, 1984 to Guillermier, disclose machines that are directed to the fitting of spokes into wheel hubs and assembly of spoked wheels. Both of these devices are applicable during the initial manufacture of spoked wheels, but are not directed to the truing of a spoked wheel.
U.S. Pat. No. 4,418,738, which issued on Dec. 6, 1983 to Kaufeldt, discloses a device for automatically tightening spokes of a spoked wheel. This device comprises a means for clamping the hub of the wheel and for engaging the outside edges of the rim. After the hub is securely clamped, the rim is secured so that it is accurately positioned on a single plane while each of a plurality of spoked nipples are tightened to an individual predetermined torque. This type of apparatus requires that the rim be securely clamped during the nipple tightening operation. Therefore, it does not provide for selectively determining the torque for each spoke based on the position of the rim portion adjacent the spoke.
U.S. Pat. No. 3,958,315, which issued on May 25, 1976 to Kinney, discloses a method of tightening the spokes of a wire wheel in which the spokes are divided into eight groups and in which four sets of two groups each are tightened in sequence. The rim of the wheel is secured during the nipple tightening operation. This method provides a procedure in which each of the nipples is first tightening to a finger-tight position and then the spokes are tightening in groups of adjacent spokes. This method does not provide a means for determining the tightness of each spoke in relation to the axial or radial position of the rim.
U.S. Pat. No. 3,908,729, which issued on Sept. 30, 1975 to Carminati, discloses a machine for securing the spoke nuts, or nipples, of a bicycle wheel while controlling the torque applied to each nut in response to the position of the nut on the wheel in relation to the order of tightening of the nuts. The torque applied is progressively greater from nut to nut, starting from the first nut, until a maximum torque is applied after the spokes over half the wheel circumference have been tightened. This device utilizes a torque regulator that performs independently from the actual position of the rim with respect to the center line of rotation of the hub and does not adjust the individual torques of each spoke in order to align the rim with respect to the axle center line.
U.S. Pat. No. 4,045,852, which issued on Sept. 6, 1977 to Winch, discloses a wheel truing machine for use with newly built spoked wheels. After the spokes of the wheel are fitted and nipples are loosely screwed onto the threaded ends of the spokes, the rim is secured in a concentric relationship with the hub. The rim is then locally depressed relative to the hub to a datum radius in the region of a nipple. The nipple is then partially tightened. This procedure is repeated until all of the nipples are tightened as desired. Since this machine exerts a force against the rim during the nipple tightening procedure, it does not permit the rim to move in response to the increased or decreased torque on each individual spoke. Therefore, when the rim is released, subsequent to the nipple tightening procedure, there is no guarantee that it will retain the desired position and relationship with respect to the central axis of the hub.
The machines and procedures for assembling and truing spoked wheels that are presently known to those skilled in the art exhibit certain significant disadvantages. These disadvantages can best be understood by comparing the known machines to the method employed during manual truing of a spoked wheel. In a typical manual truing operation, the operator first attaches the axle of a misaligned wheel to a support device. Generally, the support device is configured so that the spoked wheel is supported with its central axis of rotation disposed in a horizontal plane and the rim of the wheel disposed in a plane which is generally vertical. If the hub and rim is rotated about the fixed horizontal axle, the rim of a misaligned wheel will visually vary from a flat vertical plane and exhibit a noticeable "wobble". Using an appropriate device, such as a pointer or indicator gage, the operator then determines the approximate location of an ideal flat plane in which the misaligned rim would be disposed if it was properly aligned. After this reference plane is determined, the rim can be slowly rotated to determine the relative distortion of each portion of the rim from this ideal reference plane. Then, one by one, each spoke is either tightened or loosened to move its associated portion of the rim from its present position toward the ideal plane. As the tension on each spoke is manually adjusted, the rim of the misaligned wheel is gradually reshaped and the wheel's alignment is improved. This procedure is repeated until the rim is disposed in the ideal plane within some predetermined degree of accuracy. In order for the manual truing procedure to be performed properly, the rim of the spoked wheel is allowed to move freely in response to the increased or decreased tension on the spokes. The movement of the rim permits the operator to visually determine the individual affect of each spoke's adjustment.
Presently known machines for automatically truing spoked wheels do not accurately emulate the manual procedure described above. Instead, known techniques rigidly fasten the rim of the spoked wheel to a preselected datum plane and then tighten the nipples for each spoke of the wheel. Alternatively, some known methods attempt to achieve a constant predetermined torque on each spoke. When the rim is clamped during the tightening procedure, there is no guarantee that the rim will retain a perfectly circular and flat configuration when the clamping forces are released. Also, unless the rim is perfectly shaped in a circular and flat disposition when the spokes are loose, there is no logical reason to believe that identical torques on each spoke will achieve a properly aligned wheel. For example, assuming that the rim of the wheel has a slight oval shape in its relaxed state, identical torques on each spoke will not achieve a perfectly circular and flat rim since the rim's natural ovality must be overcome by the relative differences between the torques on the individual spokes.
The present invention aligns the spoked wheel by incorporating the successful techniques that have been used by wheelwrights to manually align spoked wheels. It supports the spoked wheel with the hub and rim being free to rotate about the center line of the axle. Therefore, the result of the tightening, or loosening, of an individual nipple can readily be determined from the position change of that portion of the rim associated with the nipple and its connected spoke. The present invention determines the direction of misalignment of each portion of the rim, in both the radial and axial directions, and adjusts the torque of the associated spoke in response to this misalignment. Means are provided for determining the axial and radial directions of the rim's misalignment proximate a spoke of the wheel. Depending on the direction of misalignment, the nipple of the spoke is rotated in either a clockwise or counterclockwise direction about the centerline of the spoke. Although, in a preferred embodiment of the present invention, each sequential nipple adjustment comprises a single revolution of the nipple, alternative magnitudes of tightening or loosening could easily be employed.
The present invention also employs a means for rotating the rim of the spoked wheel about its central axis of rotation and stopping the rim at an angular location that places a preselected spoke at an operative position for adjustment. If the associated portion of the rim exhibits a deviation from a desired reference position, a nipple adjustment means is moved into position to encompass the shank of the nipple. The nipple adjustment means comprises a clamping member that can be rotated around the center line of the spoke and the nipple's shank. This rotation causes the nipple to move in relation to the spoke in either a clockwise or counterclockwise direction, depending on the direction of rotation of the clamping member. The clamping member is mounted in a frame member that is pivotally associated with the support structure that holds the axle of the wheel. This pivotally attached frame member and associated clamping device, or member, are each provided with a slot in their structures that permits them to be moved into a position that disposes the shank of the nipple at the center line of rotation of the clamping device. After one or more complete revolutions of the clamping device, the slots are again aligned to permit removal of the frame member away from the nipple's shank.
After this adjustment of the preselected nipple, the wheel is again rotated an angular distance that disposes a subsequent nipple at the operative position. When a nipple is disposed in the operative position, the present invention determines if the associated rim portion is aligned or misaligned with respect to the predetermined ideal plane. If the rim portion at the operative position is aligned within a predetermined degree of accuracy, the wheel is continually rotated in order to dispose the next subsequent nipple in the operative position. This procedure is continued and, upon the determination of misalignment of a rim portion in the operative position, the wheel is stopped and the nipple turning mechanism is again rotated about its pivot toward the nipple's shank and the above-described tightening, or loosening, operation is again performed.
The present invention provides a means for rotatably supporting the wheel and for rotating the wheel about the central axis of its axle. A means for stopping the wheel's rotation is provided so that each nipple can be disposed at the operative position for adjustment if necessary. The present invention also comprises means for indicating locations on the wheel's rim that deviate from ideal radial or axial positions. Means for rotating the nipple is provided. The nipple rotating means is shaped to engage the outer surface of the nipple at its shank. The nipple rotating means is also provided with a slot that permits the passage of the nipple's shank toward the center line of a rotatable clamping member when the nipple rotating means is moved toward the operative position. Indicating devices are employed in cooperation with a means for actuating the nipple rotating means. These actuating means, such as limit switches, provide signals that cause the nipple rotating means, or tool, to be moved about its pivot point toward the operative position.
By tightening or loosening each nipple, in response to the actual deviation of the rim proximate the nipple, the present invention automatically performs the procedures that are normally followed by wheelwrights during manual truing operations. Furthermore, the present invention avoids the normal disadvantages that are encumbent with the use of machines that clamp the rim of a spoked wheel during the torque adjusting operations. The present invention also provides a control scheme that permits a spoked wheel to be completely aligned and adjusted without manual intervention except for the initial mounting of the wheel in the present invention and subsequent dismounting of the wheel following the termination of the automatic truing operation.